1. Field of the Invention
The invention relates to the display of images with the use of mosaic color filter patterns.
2. Description of the Related Art
The demand for full-color flat panel displays has been increasing rapidly in recent years in conjunction with the advances being made in personal computers in general and portable personal electrical products in particular. In responding to this demand, high priority is now being given to establishing means for supplying such displays at reasonable cost.
In order to provide full-color imaging, a color filter (CF) is applied. For example, in a liquid crystal device (LCD), the color filter is disposed on a display screen to alter the emitting light passing therethrough.
A number of methods are known conventionally for manufacturing RGB color filter arrays. Among them, photolithography processes provide advantages of high yield and efficiency, making such an industry choice. In such a process, red, green, and blue photosensitive compositions are coated on a substrate by spin coating. The coatings are then etched to form red, green, and blue color filter patterns on predetermined regions of the substrate. In that way, color filter arrays can be configured wherein red, green, and blue coloring layers are deployed adjacent to each other.
With this manufacturing method, the flatness of the rear color filter pattern depends on the shape of the front color filter pattern earlier formed on the substrate. For example, when the sidewall of the front color filter pattern is a discontinuous plane or has an opening, the opening interferes with the subsequent spin coating process of the rear color filter pattern. This can result in undesirable line mura defects of the full-color flat panel display employing the color filter array.
FIG. 1 is a schematic diagram depicting fabrication of a conventional color filter substrate by a spin coating process. A substrate 20 is disposed on a support 12, and a first color photoresist composition 13, provided by a dispenser 11 of a spin coater 10, is injected on the substrate 20 having a display region 22 and a peripheral region 23. After spinning the support 12 as indicated by the arrow for a few seconds, a uniform coating of the first color photoresist composition 13 is formed on the substrate 20. The coating is then patterned to form a front color filter pattern 30.
FIG. 2 is a close-up view of location L shown in FIG. 1. The front color filter pattern 30 formed on a dummy region of the peripheral region 23 has an opening 21. When forming a rear color filter pattern 40 on the display region 22, a second color photoresist composition 33 flows as indicated by the arrows over the front color filter pattern 30. Since the second color photoresist composition 33 flowing into the opening 21 of the front color filter pattern 30 is blocked by the boundary 25, a thicker rear color filter pattern 41 is formed, thereby producing an uneven rear color filter pattern 40 (comprising thicker rear color filter pattern 41 and thinner rear color filter pattern 42), further resulting in undesirable line mura defects of the full-color flat panel display. FIG. 3 is a photograph of a conventional full-color flat panel display, illustrating an example of such a line mura defect.